Perennials

Agapanthus 'Storm Cloud'

Storm Cloud Agapanthus

Amaryllidaceae

Garden hybrid of South African parentage

At a Glance

TypePerennial
HabitClumping
FoliageDeciduous
Height36-48 inches (90-120 cm)
Width18-24 inches (45-60 cm)
Maturity3 years

Growing Zones

USDA Hardiness Zones

6 - 10
Zone 6
Zone 7
Zone 8
Zone 9
Zone 10
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Attracts Butterflies
Attracts Hummingbirds
Deer Resistant
Drought Tolerant
Container Friendly
Maintenancelow

Overview

Agapanthus 'Storm Cloud' is a clump-forming, deciduous perennial reaching 36–48 inches (90–120 cm) tall including flower stalks, with clumps 18–24 inches (45–60 cm) wide. This cultivar produces deep violet-blue to dark purple flowers, darker than most Agapanthus selections. Strap-shaped, arching basal leaves are 12–18 inches (30–45 cm) long and dark green. Flower umbels are rounded, 5–7 inches (13–18 cm) across, composed of 40–60 individual tubular flowers on sturdy, erect stalks. Bloom occurs July through August. Individual umbels last 2–3 weeks; multiple stalks emerge in succession over 3–4 weeks. Foliage dies to the ground in fall in zones 6–8. Deciduous habit confers greater cold hardiness than evergreen Agapanthus cultivars, with reliable survival to zone 6 when mulched. Plants establish over 2–3 years and flower most prolifically when slightly root-bound. Fleshy roots form dense mats. Crown rot develops in waterlogged winter soils, particularly in heavy clay. Flower stalks may lean or lodge in windy, exposed sites. All parts contain calcium oxalate crystals and are toxic if ingested.

Native Range

'Storm Cloud' is a garden hybrid of South African parentage. The genus Agapanthus is native to southern Africa, with species distributed from the Western Cape through KwaZulu-Natal.

Suggested Uses

Commonly planted in perennial borders, mixed borders, and container gardens at 18–24 inch (45–60 cm) spacing. Container culture in 5-gallon (19 L) or larger pots extends the usable range into zones 4–5 with winter storage. Not suited to waterlogged soils, deeply shaded sites, or exposed windy locations where flower stalks may lodge.

How to Identify

Distinguished from other Agapanthus cultivars by deep violet-blue to dark purple flower color, among the darkest in the genus. Flower umbels 5–7 inches (13–18 cm) across on stalks 36–48 inches (90–120 cm) tall. Deciduous foliage dies to the ground in winter, distinguishing it from evergreen types. Strap-shaped leaves 12–18 inches (30–45 cm) long, dark green, narrower than those of larger evergreen cultivars.

Appearance

Size & Dimensions

Height3' - 4'
Width/Spread1'6" - 2'

Reaches mature size in approximately 3 years

Colors

Flower Colors

purple
blue

Foliage Colors

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~4 weeks
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Summer
Flowers July through August in zones 6–10. Individual umbels last 2–3 weeks; total bloom period extends approximately 4 weeks as multiple stalks emerge successively. In zone 10, bloom may begin in June. Flower production is reduced in the first 1–2 years after planting and increases as clumps mature.

Detailed Descriptions

Flower Description

Deep violet-blue to dark purple

Foliage Description

Dark green, strap-shaped, arching

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)
357912
Soil Types
loamsand
Drainage
well drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Water regularly during the first growing season. Established plants tolerate moderate drought but flower production decreases during prolonged dry periods. Crown rot develops in waterlogged winter soils; well-drained planting sites are essential, particularly in zones 6–7 where winter moisture is high. In zone 6, apply 3–4 inches (8–10 cm) of winter mulch over the crown after the first hard frost. Container-grown plants in zones below 6 require overwintering in a frost-free location. Feed with a balanced fertilizer in early spring. Divide congested clumps every 4–5 years in spring; flowering may be reduced for 1–2 years after division.

Pruning

Remove spent flower stalks at the base after bloom to redirect energy to root development. Cut back all dead foliage in early spring (March–April) before new growth emerges. No other pruning is required.

Pruning Schedule

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early spring

Maintenance Level

low

Container Growing

✓ Suitable for container growing

Minimum container size: 5 gallons

⚠️ Toxicity Warning

Toxic to pets and humans